In the raven's territory

ANOTHER LIFE:  AS USUAL in July, young starlings have conjured themselves into gangs and swoop about the hillside walls and hedges, reckless as skateboarders, skimming and swerving and putting the heart across rural pedestrians, writes Michael Viney.

They perch for a few seconds' rest on the weather-bare twigs at the top of the elder tree outside my window, briefly still and dark against the sea.

You'd wonder how the juveniles find each other, so freshly out of nests that are sparse and scattered across the townlands. But avian flocks are full of mysteries.

On several morning walks last week, I put the same small flock of young rooks to flight - young because their faces were darkly feathered, without the bare patches of skin that come later.

I used to think, along with many, that the bare skin around the bill was, as it were, a face-saving measure in the probing of soil for worms (like bare-headed vultures, digging into carrion), but, apparently, it's to let other crows know they're a flock of rooks and without territorial ambitions.

Why some birds flock and roost communally - and others don't - has been keeping biologists happy for years, and evolutionary game theorists are the latest to juggle the pros and cons of sharing information about food.

It was Bernd Heinrich, the great American student of ravens, who worked out that ravens who discover a carcass call others in to share it, not from any altruism, but to overwhelm any objection from the local resident pair. But why bother to yell if the locals haven't found it yet, and why bother to go searching at all, and maybe losing status in the flock, if someone else is going to call you for lunch?

The last time I saw a lot of ravens in July, they were circling high above the shore. In Michael Longley's lines: "This is raven's territory, skulls, bones/ The marrow of these boulders supervised/ From the upper air . . ."

But while ravens, do, of course, watch for carrion, a flock in the breeding season is likely to be non-breeding birds ganging up in what has been termed "prolonged adolescence". What better fun than to hang about in the lift of a thermal, rising above warm sand?

A reader near Bantry, Co Cork once watched about 50 ravens riding updraughts from the cliffs and engaging in the sort of pleasurable acrobatics more usually associated with their smaller relatives, the choughs. Indeed, our moorland coasts and high-cliffed islands, sprinkled with sheep left much to their own devices, breed far more ravens than most of the interior.

Many nest on the islands, feeding their young from the abundant eggs and dead chicks of the seabird colonies.

They don't always, of course, wait for their food to die. The plucking of eyes from living lambs is part of their darker reputation, though my farming neighbours would more readily indict the great black-backed gulls. And a reader fishing on Lough Corrib once watched a raven plummet into a flying mallard duck and cripple it. Another, in Co Clare, watched two ravens make a concerted and murderous attack on a little egret on the Shannon estuary.

The birds are also very fond of fish, and in the Arctic are known to perch at Inuit fishing holes in the ice, and haul up the line, bit by bit - hold on, that may not be true. But Bernd Heinrich was happy to quote an Alaskan Indian who saw an otter haul a fish on to an ice floe and then be bullied off its prey by a raven. And my drawing commemorates what did happen as I walked on our deserted strand one January morning after a gale in 1995.

A young otter emerged from the foam about 30 metres ahead, with a small fish in its mouth. It ran, in the usual humped, ungainly way across the strand and up the steep slope of the dunes, there to eat its fish in a hollow among the marram grass. A raven appeared out of nowhere and hung above the otter, claws dangling, and uttering a threatening, "Caa! Caa! Caa!"

The otter ran this way and that between the grass hummocks, its course marked by the fluttering raven. It appeared on the crest of the dune, twisting and lolloping in the soft sand, while the bird touched down nearby, wings lifted and neck stretched.

This was too much: the otter swung away and bounded down the face of the dune, still clutching its fish, and kept going until it gained the foam.

EYE ON NATURE

It is possible to drive out of Dublin and not have moths getting smashed on one's windscreen. Have the moths been affected by light pollution, a virus, disease or perhaps by telephone masts? 

Catherine Cavendish, Sandycove, Dublin

A recent report on the moth population in Britain found that large numbers of moth species are in decline. Habitat loss and climate change are suggested as among the main causes. This will affect birds, bats and several small mammals that feed on the mainly night-flying moths.

While we were on Gola Island, a basking shark kept circling slowly for three days in the cove. It was about 18 feet long and the water was so clear I could see his huge, pale, open mouth as he moved lazily in the sunlit water.

Margaret Breslin,  Bunbeg Harbour, Co Donegal

The house martins failed to return in 2006 and 2007. Out of the blue, they arrived back in the last week in June and occupied the old nests. Are they the same birds? Why are they so late?

Mary McGrath, Newbridge, Co Kildare

They may not be the same birds, and were probably at another location which didn't work out for them and then they discovered your unused nests.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo; e-mail: viney@anu.ieInclude a postal address.